Implementing remote wakeup per USB 2.0 spec

[aneves]

Hello,

While browsing the example code in lib_usb, I noticed this snippet from the included function USB_StandardRequests:

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    case USB_CLEAR_FEATURE:

        /* Device Features than could potenially be cleared are as follows (See Figure 9-4)
         * Self Powered: Cannot be changed by SetFeature() or ClearFeature()
         * Remote Wakeup: Indicates if the device is currently enabled to request remote wakeup.
               by default not implemented
         */
        break;

If I wanted to support the remote wakeup feature in my device, how would I go about using lib_usb to actually wake the host per the USB 2.0 spec? In other words, how can I tell if my device has been suspended by the host and an event has occurred where I need to wake the host to transmit data between my device and the host?

Thanks.

[infiniteimprobability]

Hi, from USB made simple (http://www.usbmadesimple.co.uk/ums_3.htm):

It is also possible for a device with its remote wakeup feature set, to initiate a resume itself. It must have been in the idle state for at least 5ms, and must apply the wakeup K condition for between 1 and 15 ms. The host takes over the driving of the resume signal within 1 ms.

So you would need to apply the K condition. The best place to work out how to do this is by looking at:

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XUD_Manager.xc

which is where you can find the signalling manager code. Eg. function

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XUD_UIFM_PwrSigFlags()/code] around line 350

[infiniteimprobability]

Ok - seems that code I pointed to you is about configuring the PHY to detect (not assert) K-state.

Looking at the datasheet, it is not entirely obvious how to assert a K. However, XUD_TestMode.xc might help:

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        case WINDEX_TEST_K:
            //Function Control Reg. Suspend: 1 Opmode 10
#if defined(ARCH_S) || defined(ARCH_X200)
            write_periph_word(USB_TILE_REF, XS1_GLX_PERIPH_USB_ID, XS1_UIFM_FUNC_CONTROL_REG, 0b1000);
#else
            XUD_UIFM_RegWrite(reg_write_port, UIFM_REG_PHYCON, 0x11);
#endif

            while(1)
            {
                p_usb_txd <: 0;
            }
            break;

[aneves]

Thanks for the reply, but how can I detect that my device has been suspended by the host?

[infiniteimprobability]

There's a pair of callbacks called void XUD_UserSuspend() and void XUD_UserResume(). They are weak functions so just go ahead and define your own to override them. They are called from the XUD (USB) thread so you may want to set a shared memory flag or perhaps output over a channel end (perhaps use a pointer to global channel end to avoid passing a chanend all the way through the xud API).

[aneves]

Cool, thanks!